AC power anomalies disrupt only phono stage?

Despite the insertion of a Power Conditioner (Shindo Mr T) for the turntables and preamp in my system……when the street’s power supply is corrupted, the phono stage of my Halcro DM10 preamp is rendered virtually unlistenable?
At the same time…..the line-level inputs (like Tuner and Aux) are unaffected. In fact the sound through the TV (connected to Aux)…..is quite sublime on movie scores.

I am baffled at what could possibly cause the phono-stage to ‘implode’ at these times…..whilst leaving untouched the high-level stages?